1. Field of the Invention
The present invention relates to a seat belt retractor for vehicles to protect an occupant and more particularly to a seat belt retractor in which a seat belt thereof is in contact with the occupant with light pressure while it is fastened and it is retracted strongly when it is retracted into the retractor.
2. Description of the Related Art
As is commonly known, a seat belt retractor is designed to restrain an occupant by unwinding a seat belt from a retractor provided in a vehicle and engaging a tongue of the seat belt into a buckle.
In the seat belt retractor, the seat belt withdrawn from the retractor has usually tension from the retractor in the retracting direction thus enabling the seat belt to fit the occupant.
However, because the seat belt is in constant contact with the occupant, when the tension of the belt is too large, the seat belt restrains the occupant too strong so that the occupant feels uncomfortable. On the contrary, when the tension of the belt is too weak, the retractor retracts the seat belt slowly.
To solve these problems, Japanese Utility Model Publication No. 57-20212 proposes a seat belt retractor which comprises a rotatable spring case connected to a seat belt retracting reel shaft through a helical spring, and an externally operable adjusting gear engaging with gear teeth formed in an outer surface of the spring case so as to enable to adjust retracting force of the helical spring.
However, the seat belt retractor disclosed in Japanese Utility Model Publication No. 57-20212 has the reel shaft energized by a single power spring, so that energizing or spring force of the retractor is adjusted solely by this single power spring. Therefore, a range of adjusting the retracting force for the seat belt is relatively narrow. As a result, the seat belt retractor of the Utility Model can not substantially meet the following contradictory requirements: Namely, eliminating restrained feeling of the occupant while wearing the seat belt and enlarging the retracting force of the seat belt.